Electric heating element.



v E. J. ROHNE.

ELECTRIC HEATING ELEMENT.

APPLICATION IILBD on. so, 1913.

1,1 33,579. Patented Mar. 30,- 1915. 2 sums-sum 1.

i 2 A E i k I i ii 12K m/Z/ a a? WW @MZQ mzZemm 111M413 E. J. ROHNE.ELECTRIC HEATING ELEMENT. APPLICATION FILED OUT. so, 1913.

1,133,579. Patented Mar. 30, 1915 2 SHEETSSHEET 2.

Jig. J

UNITE STATES PATENT OFFICE EVEN J. ROHNE, 0F MINNEAPOLIS, MINNESOTA.

ELECTRIC HEATING ELEMENT.

Application filed October 30, 1913.

To all whom it may concern:

Be it known that I, EVEN J. ROHNE, a citizen of the United States,residing at Minneapolis, in the county of Hennepin and State ofMinnesota, have invented certain new and useful'lmprovements inElectrical Heating Elements; and I do hereby declare the following to.be a full, clear, and exact description of the invention, such as willenable others skilled in the art to which it appertains to make and usethe same.

My invention has for its object to provide an improved electric elementadapted to be used as a heating device, and to such ends, generallystated, the invention consists of the novel devices and combinations ofdevices hereinafter described and defined in the claim. I

In the accompanying drawings which illustrate the invention, likecharacters indicate like parts throughout the several views.

Referring to the drawings, Figure 1 is a diagrammatic plan view of theimproved device; Fig. 2 is a fragmentary view of the.

fabric body of the pad; Fig. 3 is a view partly in plan and partly insection with some parts broken away, showing plug and switch connectionsand a fragment of the pad; Fig. 4 is a detail view in plan showing onesection of the controlling switch; and Fig. 5 is an enlarged fragment ofone of the coils and its core.

The body 1 of the pad, the outline of which is shown by dotted lines inFig. 1, is a flexible member, the body or main element of which is acoarsely woven fabric consisting of warp threads 1, main woof threads 1"and addition or auxiliary woof threads 4, which latter, in accordancewith my invention, serve as cores for coils 2 and 3, and are made fromsoft pliable non-conducting material, such as asbestos yarn.

The coils 2 and 3 are made from very fine wire and are tightly woundaround the soft and flexible non-fusible cores 4, in such a way thatthey are practically embedded therein, and nearly or quite covered bythe fibrous surface of the said cores, (see particularly Fig. 5). Inthis way, also, the coils are made to take up a great deal of wire witha comparatively short core.

The distinctive feature of this invention is the employment of a pliableinsulating core in connection with a wire that is, per se, bare, ornon-insulated but is spirally wound around the said core and drawn intothe Specification of Letters Patent.

Patented Mar. 30, 1915.

Serial No. 798,903.

same so that its convolutions are not only held out of contact, but aresunken into the core and protected from contact with externallyconducting surfaces.

The numeral 5 indicates an ordinary electric plug adapted to be screwedinto an ordinary electric socket. This plug is provided with two leadwires 6 and 7.

The wires 6 and 7 lead to a switch, the body of which is preferably madeup of two cap-like members 8 and 9, the latter being swiveled on atubular hub 10 of the former, and held against axial displacement by acollar 11 on the projecting end of the said hub. Both of the sections 8and 9 are preferably constructed of wood fiber, vulcanized rubber, orother suitable insulating material. Within the member 8 is an annularcore 12 of insulating material, and on which are wound three separatedterminal coils 13, 14 and 15 that constitute contact pieces adapted tobe engaged by a segmental contact 9 located within and carried by thecap 9.

The wire 6 from the plug 5 is an insulated wire which extends axiallythrough the switch, without electrical connection therewi th, and isconnected with one end of the coll 2. The other terminal of the coil 2is connected by a wire 16 to the contact coil 13. The plug wire 7 isconnected to the contact coil 15. One terminal of the coil 3 isconnected by a wire 17 to the contact coil 14, and the other terminal'of the said coil 3 is connected to the wire 16, all as clearly shown inFig. 4. 4

By rotary movement of the cap 9, the segmental contact' 9 may be causedto simultaneously engage the coils 13, 14 and 15, or it may be engagedonly with the contacts 14 and 15. \Vhen the said contact 9' is engagedonly with the contact coils 14 and 15, the flow of the current will beas follows: through wire 6, heating coil 2, heating coil 3, and wire 17to contact coil 14, and from thence, through contact 9, contact coil 15and wire 7, back to plug 5. Under these conditions, the current cannotshort circuit from heating coil 2 through the wires 16 and coil 13, andhence, must pass through both of the heating coils 2 and 3. Otherwisestated, the two heating coils 2 and 3 are then connected in series sothat they afford a rent, and hence, produce a relatively low maximum ofresistance to the electric curheating effect.

When the-contact 9 is connected to all three of the contact coils 13,Hand 15, the flow of current will be as follows: from plug 5 throughwire 6, heating coil 2,-wire 16, contact coil 13, contact 9 and wire 7,back to plug 5. It will be noted that at this time the circuit is alsoclosed through coil 3 but that all current which passes through thelatter must first pass through the coil 2, so that, in fact, very littlecurrent will pass through the said coil 3 and the said coil- 3 ispractically thrown out of action, because the current taking the path ofleast resistance, will pass from the coil 2 back through wires 16 andother connections noted. In this adjustment of the switch, a much lowerelectrical resistance is offered to the current than with the previouslynoted adjustment, and consequently, more current will flow with theresulting higher heating efiiciency. Obviously, when the contact 9 isturned out of engagement with the contact coils 13, 14 and 15, orv intoengagement only with one thereof, no current, whatever, will flowthrough the heating coils 2 or 3.

What I claim is:

An electrical heating element comprising a core of pliable insulatingmaterial, and a wire that is, per se, bare but is wound around the saidcore and drawn completely into the

